Letting my kids sit in boxes. The first day I started taping boxes together it went like this. Tape up a box..."Silas, Mommy needs to put something besides you in the box"..."nevermind"...Tape up another box..."Silas, what happened to the last box I taped up? I need this box, dear"..."Forget it"....go get the last box I taped..."Hi Gideon, are you have fun in Mommy's boxes"...leave them alone and tape another box.
Bubble wrap...seriously, I know adults who can't resist the stuff
Old pictures. This occupied my boys for quite a while, but I didn't get much done while they were looking because I wanted to look to.
Last but not least, Toy Story 1 on you tube...even after the TV and DVD player where on their way to the new place I could put the boys in front of the lap top. It kept them out of the way and safe while we were carrying the other big stuff down the steps.